The aims of this project are to identify immune complexes in the renal glomerular basement membranes of patients with malignancies, and to determine the specificities of the tumor-directed antibody component. Initial examination by electron microscopy and immunofluorescence of kidneys of cancer patients with no clinical renal disease has shown evidence of immune complex deposits in approximately 30 percent. These patients had both epithelial and lymphoreticular malignancies. Granular, electron-dense complexes were consistently located on the endothelial side of the glomerular basement membrane. Immunofluorescent staining showed the presence of IgG, IgA and complement. Portions of kidneys are then processed to yield a highly purified glomerular suspension which is sonicated and eluted with potassium iodide. Globulins in the eluates are precipitated with ammonium sulfate redissolved and concentrated. The globulin fractions of individual eluates reacted with cryostat sections of unfixed, autologous and heterologous tumors, but not with non-neoplastic tissues. Portions of the globulin fractions were also tested by radial immunodiffusion which showed the presence of IgG and IgA, and by Sephadex G-200 column chromatography which showed the tumor-directed fraction to be in the 150,000 dalton molecular weight range. Further studies are designed to assess the activities of the eluates in lymphocyte cytotoxicity preparations and to identify the antigens eliciting the humoral immune response to these cancers.